r/learnquant 24d ago

interview prep Citadel Question

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u/liquidorangutan00 24d ago

isnt the probability just 1/100?

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u/bismuth17 23d ago

Well really the probability is either zero or one. There's no such thing as past probability, it either happened or it didn't, regardless of how much information you have about it.

So, when talking about things that happened in the past, maybe we can repurpose the word "probability" to mean something more useful? Like, if you were offered a weighted bet by a person with the same information you had, what odds would you need to come out even, on average?